Evaluation of the Soil Moisture Operational Estimates From SMOS in Europe: Results Over Diverse Ecosystems

This study presents the results of an extensive validation of the Soil Moisture and Ocean Salinity mission (SMOS) soil moisture operational product from selected European sites representative of a variety of climatic, environmental, biome, and seasonal conditions. SMOS soil moisture estimates were compared against corresponding in-situ measurements from the CarboEurope observational network. The agreement between the two datasets was evaluated on the basis of a series of statistical metrics. In addition, the effect of variability of site characteristics such as land cover, seasonality, and also that of the Radio Frequency Interference (RFI) effect on SMOS was explored. In overall, the SMOS soil moisture product estimates agreed reasonably well with near concurrent CarboEurope in-situ measurements acquired from the 0-5 cm soil moisture layer. Significant changes in the SMOS performance were observed with local adjustments, such as land cover and seasonal changes. Agreement was found to be higher over low vegetation cover and during the autumn season. The RFI contaminated pixels were filtered out from the pooled datasets, as well as from the seasonally discriminated datasets, which resulted in noticeably improved performances. This paper provides strong supportive evidence of the potential value of the SMOS soil moisture product for hydrometeorological and related studies.